The Securities and Exchange Commission says a corporation owned by a prominent Canadian investment family, already charged with violating SEC filing requirements, committed similar violations two months earlier.

The SEC said First City Financial Corp. Ltd., the corporation of the wealthy Belzberg family of Vancouver, British Columbia, used a major Wall Street brokerage firm to conceal its takeover attempt of Hartmarx Corp. in December 1985 and January 1986.

The Hartmarx case was "virtually identical" to First City's attempt to take over Ashland Oil Co. in February and March 1986, the SEC said, and disproved First City's contention that the Ashland case represented a simple misunderstanding.

First City did not return two telephone calls seeking comment yesterday.

The SEC made the argument in a filing in U.S. District Court here urging Judge Barrington D. Parker to deny First City's motion to dismiss a civil complaint against it.

The SEC has charged First City and Marc Belzberg, a vice president of First City and son of its founder and chairman, with violating takeover regulations by illegally "parking" shares of Ashland Oil with Bear, Stearns & Co.

The SEC contended that Belzberg directed the Wall Street firm to buy and hold Ashland shares to conceal First City's ownership.

Federal regulations require investors to disclose their ownership when they acquire 5 percent of a company's stock. But the SEC contended Bear Stearns Chairman Alan Greenberg spent $14 million buying Ashland stock for First City.

The stock was held in a house account so it would not appear in the Belzbergs' name, but First City assumed all risk and expense, the SEC contended.

Counting the Bear Stearns holdings, the SEC said, First City passed the 5 percent threshold on March 4, and was required to file a disclosure by March 14. Instead, the SEC said, First City acquired an additional 890,000 shares, pushing its stake to 9.2 percent by March 25, when its holdings were disclosed. The stock price then soared.

On April 2, First City sold the shares back to Ashland at a $15 million profit, the SEC stated. First City is known in financial circles as a skilled practitioner of "greenmail," the SEC said, in which an investor abandons a takeover attempt when the target company offers to buy out his stake, sometimes for a premium price.

In a motion filed earlier, the defendants asked Parker to dismiss the "parking" charges, contending that Greenberg had misunderstood a casual suggestion by Belzberg that Bear Stearns acquire its own shares of Ashland.

Disputing that motion, the SEC said First City and Bear Stearns made virtually identical arrangements in a takeover run at Hartmarx two months earlier.